Data and information for Problems $4-6$

Flocculation tanks are to be designed to treat a total flow rate of $49,200\frac{m^3}{?}$ day. The following design conditions apply to the design: water temperature of $20C,$ total mean detention time of $45$ minutes, basin depth of $3\mathrm{.}5m.$ There are to be three parallel treatment trains, with each receiving one third of the total flow. Each treatment train will be comprised of three flocculation stages each of which will be the same size $($so$,$ a total of nine flocculators, see diagram below$).$ Tapered flocculation will be employed with $G=50se{c}^{-1}$ in the first stage and $G=35se{c}^{-1}$ in the second stage.

$4.$ If the width of each flocculation basin is $7\mathrm{.}0$ meters, the length $($in units of meters$)$ of each of the nine flocculation compartments should be most nearly?

A$.3\mathrm{.}5$

B$.7\mathrm{.}0$

C$.15$

D$.21$

E$.495$

$5.$ The power input into the first flocculation compartment of each of the three parallel treatment trains $($W$)$ should be most nearly?

A$.6\mathrm{.}9{10}^1$

B$.2\mathrm{.}1{10}^2$

C$.4\mathrm{.}3{10}^2$

D$.5\mathrm{.}6{10}^2$

E$.1\mathrm{.}3{10}^3$

$6.$ If the power input to the last compartment of each of the parallel treatment trains is $70W,$ the velocity gradient $(se{c}^{-1})$ will be most nearly?

A$.12$

B$.18$

C$.20$

D$.22$

E$.24$